I can imagine what Iwata would say and what would happen during Shulk's trailer.
"Our final announcement comes from our colleagues from Monolith Soft and a project they are working on. But first, they want to show you some special footage that they just received. Please take a look."
We see Shulk standing in the Gaur Plains, looking at the Mechonis. Then Shulk has a vision of an odd group of monsters attacking Colony 9. Shulk rushes towards Colony 9 to see that Bowser and his minions are attacking his home. Shulk then quickly and effortlessly defeats Bowser and he gets into a pose with the text saying, "Shulk envisions the battle!"
Oh, and of course,
this theme plays when that happens. We see some gameplay footage of Shulk using various Monado Arts like Shield and Cyclone and his other Arts like Back Slash and Air Slash.
Near the end, we see Shulk fighting Donkey Kong, Luigi, and King Dedede. The music slightly lowers when he has a vision of getting sent flying by Donkey Kong's Giant Punch, then getting flung higher into the air by Luigi's Super Jump Punch, and finally King Dedede smashing him downward with his Super Dedede Jump. After he sees these visions, Shulk dodges Donkey Kong's attack, slashes Luigi away, and completely dodges King Dedede and attacks him with a Back Slash. After that, Shulk says, "Behold the power of the Monado!"
The SSB4 logo then comes up and the trailer ends with Shulk putting away the Monado saying, "That was too easy."
Afterwards, we see Iwata presenting another trailer for X.